Interpretive Summary: Soils of the southeastern USA have been historically degraded with intensive cultivation that resulted in loss of topsoil and poor fertility. Conservation agricultural management has the potential to build soil fertility, restore soil functions, and mitigate greenhouse gas emissions as a consequence of surface soil organic matter accumulation. A scientist from the USDA Agricultural Research Service in Watkinsville Georgia synthesized recent literature from the southeastern USA to (1) obtain an average rate of soil organic carbon sequestration with conservation agricultural management (conservation-tillage cropland and establishment of perennial pastures), (2) evaluate how surface-soil organic carbon accumulation restores soil functions, and (3) recommend practical soil sampling strategies based on spatial and temporal issues to improve the detection of statistically significant soil organic carbon sequestration. Surface accumulation of soil organic carbon was common under conservation agricultural management and appears to be integrally linked to the rate of soil organic carbon sequestration, abatement of soil erosion, and improvement in water quality. Sampling of conservation management systems should ideally occur repeatedly with time in controlled and replicated experiments, but there is also an urgent need for soil sampling campaigns on working farms to validate and expand the scope of inference of experimental results. With 111 million acres of agricultural land in the southeastern USA, 113 million tons of CO2/year could be reasonably calculated as potentially sequestered in soil organic matter. Landowners in the southeastern USA have great potential to restore soil fertility and mitigate greenhouse gas emissions with adoption of and improvement in conservation agricultural systems.

Technical Abstract:
Conservation management of degraded land has the potential to build soil fertility, restore soil functions, and mitigate greenhouse gas emissions as a consequence of surface soil organic matter accumulation. Literature from the southeastern USA was synthesized to (1) quantitatively evaluate soil organic C (SOC) sequestration with conservation agricultural management, (2) evaluate the impact of surface-SOC accumulation on restoration of soil functions, and (3) recommend practical soil sampling strategies based on spatial and temporal issues to improve the detection of statistically significant SOC sequestration. Soil organic C sequestration was 0.45 + 0.52 Mg C ha-1 yr-1 (n = 148) with conservation-tillage compared with conventional-tillage cropland. Establishment of perennial pastures sequestered 0.86 + 0.64 Mg C ha-1 yr-1 (n = 34). Stratification of SOC with depth was common under conservation agricultural management and appears to be integrally linked to SOC sequestration, abatement of soil erosion, and improvement in water quality. Sampling of conservation management systems should ideally occur repeatedly with time in controlled and replicated experiments, but there is also an urgent need for chronosequence and paired-field surveys of SOC from working farms in the region to validate and expand the scope of inference of experimental results. Landowners in the southeastern USA have great potential to restore soil fertility and mitigate greenhouse gas emissions with adoption of and improvement in conservation agricultural systems.